The antimicrobial activity of methanolic leaf extracts and crude alkaloid extracts of A. wilkesiana cv. macafeeana was evaluated after a preliminary phytochemical screening of the leaf extracts. The standard agar well diffusion method was used in the bioassay involving test bacteria and yeast isolates, while percentage inhibition of extracts on radial growths of the molds was determined. The Minimal Inhibitory Concentrations (MIC) and Minimal Bactericidal Concentrations (MBC) were also determined by the broth microdilution assay technique. The microorganisms used were clinical strains of Escherichia coli, Salmonella typhi, Streptococcus pyogenes, Strept. pneumonia, Methicillin-Resistant Staphylococcus aureus (MRSA), non-methicillin resistant Staph. aureus, Candida albicans, Aspergillus fumigatus and A. flavus. Alkaloids, tannins, terpenoids and cardiac glycosides were extracted by the methanol solvent. The crude alkaloid extracts inhibited only the Gram-negative bacteria with mean inhibition zones of 10.0±0.00 to 12.3±0.03 mm while the methanol extracts inhibited all other test organisms, a broad spectrum activity. The water extracts had no activity against the non-MRSA strains. The MIC was 0.4 mg mL^-1 for all unicells except strains of C. albicans which both had MICs of 0.8 mg mL^-1. The MBC was 0.4 mg mL^-1 for tested isolates except the non-MRSA and C. albicans which had MBCs of >12.0 mg mL^-1 and 1.0 mg mL^-1, respectively. The methanolic extract totally inhibited all tested aspergilli while the water extract had a varying inhibitory effect (63.0±2.50 to 81.0±2.90%) on the tested fungi strains. The alkaloid had no effect on the molds.